Implement Rip::Core::Base#symbols and Rip::Utilities::Scope#symbols

Also implement Rip::Utilities::Scope#to_s to make debugging easier
Refactor Rip::Nodes::BlockBody#interpret test to actually produce a side-effect
Refactor Rip::Core::Class#interpret to correctly assign references to the class

Also implement Rip::Nodes::BlockBody#interpret_with_block and Rip::Core::Class#resolve
Start convention of passing optional block to #interpret

Merge Rip::Nodes::BlockBody#interpret_with_block into Rip::Nodes::BlockBody#interpret
Predefine `self` inside classes to point to the class
Implement RSpecHelpers#{build_ast,debug_ast} to help when testing
Refactor Rip::Nodes::Class#interpret to assign to class and class prototype
Totally refactor test for Rip::Nodes::Class#interpret
Support namespaces via nested classes
Interpret classes and populate class-level and instance-level properties